High-redshift Galaxy Candidates at z = 9-10 as Revealed by JWST Observations of WHL0137-08

We report the discovery of four galaxy candidates observed 450-600 Myr after the Big Bang with photometric redshifts between z ~ 8.3 and 10.2 measured using James Webb Space Telescope (JWST) NIRCam imaging of the galaxy cluster WHL0137-08 observed in eight filters spanning 0.8-5.0 μm, plus nine Hubble Space Telescope filters spanning 0.4-1.7 μm. One candidate is gravitationally lensed with a magnification of μ ~ 8, while the other three are located in a nearby NIRCam module with expected magnifications of μ ≲ 1.1. Using SED fitting, we estimate the stellar masses of these galaxies are typically in the range $\mathrm{log}{M}_{\star }/{M}_{\odot }$ = 8.3-8.7. All appear young, with mass-weighted ages <240 Myr, low dust content A _V < 0.15 mag, and specific star formation rates sSFR ~0.25-10 Gyr^-1 for most. One z ~ 9 candidate is consistent with an age <5 Myr and an sSFR ~10 Gyr^-1, as inferred from a strong F444W excess, implying [O III ]+H β rest-frame equivalent width ~2000 Å, although an older z ~ 10 object is also allowed. Another z ~ 9 candidate is lensed into an arc 2.″4 long with a magnification of μ ~ 8. This arc is the most spatially resolved galaxy at z ~ 9 known to date, revealing structures ~30 pc across. Follow-up spectroscopy of WHL0137-08 with JWST/NIRSpec will be useful to spectroscopically confirm these high-redshift galaxy candidates and to study their physical properties in more detail.